Add comment referencing Django CSRF docs.
Add comment referencing Django CSRF docs.

mrpau/kolibri,indirectlylit/kolibri,mrpau/kolibri,indirectlylit/kolibri,learningequality/kolibri,learningequality/kolibri,lyw07/kolibri,learningequality/kolibri,indirectlylit/kolibri,mrpau/kolibri,mrpau/kolibri,lyw07/kolibri,lyw07/kolibri,indirectlylit/kolibri,learningequality/kolibri,lyw07/kolibri